As insulating films to be used as a copper diffusion barrier film in a VLSI (very large scale integration) having copper interconnects, a SiN film, a SiON film, a SiC film, a SiCO film and the like are conventionally known, and all of these films have a high dielectric constant of 4 or more. Therefore, in a multilayered interconnect structure, even when a low dielectric constant film is used as an interlayer dielectric film, the influence of the dielectric constant of the insulating film used as the copper diffusion barrier film is dominant. Accordingly, the effect to lower the dielectric constant by an interlayer dielectric film made of a low dielectric constant film in a multilayered interconnect structure is canceled by the dielectric constant of an insulating film used as the copper diffusion barrier film, and hence, a sufficiently low value has not been realized as the effective dielectric constant of the whole multilayered interconnect structure.
In order to cope with such a problem, it is necessary to lower the dielectric constant of an insulating film used as the copper diffusion barrier film or to provide an interlayer dielectric film made of a low dielectric constant film with a function as a copper diffusion barrier film.
As conventional technique to lower the dielectric constant of a copper diffusion barrier film, a method for forming a SiCN film through plasma CVD using trimethyl vinylsilane has been reported, and this SiCN film has a dielectric constant of 4. Alternatively, a method for forming a low dielectric constant interlayer dielectric film having a function as a copper diffusion barrier film through plasma CVD using divinylsiloxane bis-benzocyclobutene has been reported, and this interlayer dielectric film has a dielectric constant of approximately 2.7 (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent No. 3190886